The National Meteorological Office (Onamet) of the Dominican Republic Monday increased the alert level for tropical storm Tomas.
Onamet said the storm could become a hurricane in the coming hours when it moves from Altagracia province in the east to Pedernales province in the south.
Onamet also said it is working together with aid organizations to take all measures necessary to prepare for the upcoming hurricane.
According to Onamet, the maximum speed of the storm will be between 200 to 280 km when reaching southern Barahona province on Thursday and Friday.
On Monday, the sea waves in Santo Domingo reached 4 meters high.
Onamet said there would be an accumulated rain of about 150 mm which could possibly cause flooding in the area.
General Juan Manuel Mendez, director of the Emergency Operations Center (COE), said the COE is keeping the beaches closed.
Meanwhile, some 30 state organizations are prepared to help families which may be affected by the storm, especially those in the southern provinces.